1. Field of the Invention
The invention relates to high speed tripping devices used in small apparatus providing protection against short circuits. These devices comprise a coil associated with a magnetic circuit having a yoke, a fixed core and a low inertia mobile core for mechanically controlling the break of the associated protection apparatus, these cores being separated by an air gap placed in the region of maximum flux.
2. Description of the Prior Art
It is known to form such tripping devices with a flat mobile core so as to reduce the thickness of the associated protective device. However, these devices need to be improved as far as their simplicity and manufacturing costs are concerned.
Moreover, it is desirable to obtain in a high speed trip a substantially constant force of attraction as a function of the variation between the fixed core and the mobile core; now, in known tripping devices, this constant level of the force of attraction cannot be obtained because of the presence, on the side of the cores, of walls parallel to the direction of movement of the mobile core; or else it can only be obtained at the price of complex arrangements. The aim of the present invention is especially to optimize in a very simple manner the evolution of the force of attraction produced between the fixed core and the mobile core as a function of their air gap. Another aim is to facilitate the construction, with a saving of space and reduced cost, of a high speed tripping device for a protection apparatus of small thickness.